The invention relates to a method of polymerizing olefins.
In many circumstances, it is desirable to reduce the hydrogen effect in the presence of olefins in certain polymerization processes. When hydrogen is employed to produce polymers having low molecular weight, the hydrogen must be removed before producing high molecular weight polymer in the same reactor. In a commercial operation this is time consuming and expensive. Transition times of greater than 24 hours may be required.
When producing polymer, it is often desirable to incorporate comonomer exclusively in a high molecular weight component of the polymer. When using reactors in series, a low molecular weight polymer can be produced in a first reactor in the absence of comonomer. High molecular weight polymer can be produced separately in second reactor where comonomer is incorporated.
When using Ziegler type catalyst systems, very high concentrations of hydrogen are required to produce the low molecular weight component. However, hydrogen is detrimental to the production of high molecular weight polymer, and it is necessary that hydrogen be removed before high molecular weight polymer containing copolymer can be produced. If two reactors are employed, an intermediate separation facility between reactors is required. If a single reactor is employed, a very long transition time between polymerizations is required. These processes are expensive, mechanically complicated and perhaps infeasible with loop reactor technology.